JP2006-166498A describes a known manufacturing method of a laminated rotor iron core. According to JP2006-166498A, the manufacturing method of the laminated rotor iron core includes a process for pressing a metal plate and forming a belt iron core pieces and a process for spirally wrapping and laminating the belt iron core pieces and mutually caulking and coupling the laminated belt iron core pieces. The belt iron core pieces have a shape of the laminated rotor iron core linearly developed. The belt iron core pieces have a cutout formed at a side edge corresponding to an inner circumference at a predetermined interval. The circular side edge corresponding to the inner circumference between the adjacent cutouts corresponds to an inner circumference of a shaft hole. The belt iron core pieces have a magnet mounting hole or a diecast metal filing hole formed in the middle in the width direction at the predetermined interval. A side edge corresponding to an outer circumference of the belt iron core pieces are locally pressed and expanded when the belt iron core pieces are spirally wrapped. When the belt iron core pieces are spirally wrapped, because the cutout is formed at the predetermined interval, the side edge corresponding to the inner circumference can be bended without exerting plate compressive force on the side edge corresponding to the inner circumference and the belt iron core pieces can be wrapped to a circular shape.
However, according to the known manufacturing method of the laminated rotor iron core described in JP2006-166498A, because the belt iron core pieces are locally pressed and expanded when the belt iron core pieces are spirally wrapped and laminated, partial deformation and embossment tend to be formed when an outer circumferential side of the belt iron core pieces is bended and ensuring precision tends to be difficult. Further, for minimizing the deformation of the outer circumferential side of the belt iron core pieces, the belt iron core pieces need a large cutout and a complex shape with consideration to the deformation. However, the large cutout and the complex shape of the belt iron core pieces tend to cause low yield rate of the belt iron core pieces (material of the laminated rotor iron core) and large and expensive punch die set for forming the belt iron core pieces. Further, other than the punch die set, a loading device for loading the belt iron core pieces and a wrapping unit for wrapping and laminating the belt iron core pieces are separately needed for spirally wrapping and laminating the belt iron core pieces.
A need thus exists for a method for manufacturing a laminated rotor core which is not susceptible to the drawback mentioned above.